refactor(frontends/lean): do not expose unnecessary functions
refactor(frontends/lean): do not expose unnecessary functions

javra/lean,Kha/lean,fpvandoorn/lean2,Kha/lean,rlewis1988/lean,digama0/lean,fgdorais/lean,dselsam/lean,levnach/lean,UlrikBuchholtz/lean,c-cube/lean,johoelzl/lean,digama0/lean,fgdorais/lean,soonhokong/lean-windows,johoelzl/lean,sp3ctum/lean,sp3ctum/lean,fgdorais/lean,leodemoura/lean,leanprover/lean,leodemoura/lean,digama0/lean,soonhokong/lean-windows,leanprover-community/lean,rlewis1988/lean,avigad/lean,javra/lean,Kha/lean,soonhokong/lean,soonhokong/lean-windows,Kha/lean,fpvandoorn/lean2,johoelzl/lean,leodemoura/lean,leanprover/lean,UlrikBuchholtz/lean,avigad/lean,soonhokong/lean,htzh/lean,fpvandoorn/lean2,soonhokong/lean-osx,fgdorais/lean,soonhokong/lean-osx,leanprover/lean,fpvandoorn/lean,c-cube/lean,javra/lean,fpvandoorn/lean,leodemoura/lean,eigengrau/lean,dselsam/lean,dselsam/lean,fpvandoorn/lean,dselsam/lean,leodemoura/lean,rlewis1988/lean,eigengrau/lean,fpvandoorn/lean2,levnach/lean,fgdorais/lean,UlrikBuchholtz/lean,c-cube/lean,htzh/lean,soonhokong/lean-windows,avigad/lean,c-cube/lean,fgdorais/lean,fpvandoorn/lean2,fpvandoorn/lean,eigengrau/lean,c-cube/lean,soonhokong/lean,rlewis1988/lean,leanprover/lean,sp3ctum/lean,johoelzl/lean,leanprover/lean,avigad/lean,fpvandoorn/lean,levnach/lean,leanprover-community/lean,levnach/lean,leanprover/lean,javra/lean,eigengrau/lean,javra/lean,rlewis1988/lean,rlewis1988/lean,leanprover-community/lean,soonhokong/lean-osx,sp3ctum/lean,digama0/lean,htzh/lean,Kha/lean,levnach/lean,soonhokong/lean,eigengrau/lean,johoelzl/lean,fpvandoorn/lean,avigad/lean,avigad/lean,leodemoura/lean,soonhokong/lean,digama0/lean,leanprover-community/lean,soonhokong/lean-windows,leanprover-community/lean,soonhokong/lean-osx,digama0/lean,johoelzl/lean,soonhokong/lean-osx,UlrikBuchholtz/lean,UlrikBuchholtz/lean,leanprover-community/lean,Kha/lean,htzh/lean,dselsam/lean,sp3ctum/lean,dselsam/lean,htzh/lean